Hydrological modeling of catchment specific runoff-response to variable land-use/climatic conditions and trend-based hypothetical scenario generation: a study on a large river basin in Eastern India

The present study is an attempt toward the quantification of the impact of climate and land-use change on the hydrological prospect of the Kangshabati river basin of West Bengal. The study also simulates runoff characteristics as a response to hypothetical climatic scenarios. The scope of the study involves, first, to quantify the relative contribution of climate change and land-use change to runoff response and second, to simulate runoff characteristics as a response to hypothetical climatic scenarios. Using a combination of the SWAT model, SWAT Cup, Sequential Mann Kendall Trend Tests, surface and total runoff were generated for 1982–2017, and the mutation point was identified. The results indicate that post-2010, climate change has an overwhelming impact on runoff with its contribution being as high as 99% in the case of total runoff and 89% for surface runoff. And this finding is cemented by dynamic contribution analysis which indicates over-arching climatic impact for every decade, with a sudden increase post-2010. Change in temperature and rainfall has an expected impact on runoff, with a rise in rainfall and decrease in temperature resulting in the higher runoff than the normal, except beyond 2 °C, post which there is a sudden increase in surface runoff response, even in scenarios where there is a decrease in rainfall. While surface runoff rises 2% for every 1% increase in precipitation and decreases by 1.7% for every 1% decrease, the corresponding change for total runoff is 1.4%. The novelty of the work lies in its capacity to provide a rapid framework to the immediate stakeholders in understanding runoff response to different change-based scenario independently and in combination.